As wireless communication systems such as cellular telephones, satellite, and microwave communication systems become widely deployed and continue to attract a growing number of users, there is a pressing need to accommodate a large and variable number of communication subsystems transmitting a growing volume of data with a fixed resource such as a fixed channel bandwidth accommodating a fixed data packet size. Traditional communication system designs employing a fixed resource (e.g., a fixed data rate for each user) have become challenged to provide high, but flexible, data transmission rates in view of the rapidly growing customer base.
The third Generation Partnership Project Long Term Evolution (“3GPP LTE”) is the name generally used to describe an ongoing effort across the industry to improve the Universal Mobile Telecommunications System (“UMTS”) for mobile communications. The improvements are being made to cope with continuing new requirements and the growing base of users. Goals of this broad-based project include improving communication efficiency, lowering costs, improving services, making use of new spectrum opportunities, and achieving better integration with other open standards, and backwards compatibility with some existing infrastructure that is compliant with earlier standards. The project envisions a packet-switched communications environment with support for such services as VoIP and MBMS. MBMS may support services where base stations transmit to multiple user equipment simultaneously, such as mobile televisions or radio broadcasts, for example. The 3GPP LTE project is not itself a standard-generating effort, but will result in new recommendations for standards for the UMTS.
The UMTS Terrestrial Radio Access Network (“UTRAN”) includes multiple Radio Network Subsystems (“RNS”), each of which contains at least one Radio Network Controller (“RNC”). However, it should be noted that the RNC may not be present in the actual implemented systems incorporating Long Term Evolution (“LTE”) or UTRAN (“E-UTRAN”). LTE may include a centralized or decentralized entity for control information. In UTRAN operation, each RNC may be connected to multiple Node Bs, which are the UMTS counterpart to Global System for Mobile Communications (“GSM”) base stations. In E-UTRAN systems, the eNode B may be, or is, connected directly to the access gateway (“aGW,” sometimes referred to as the services gateway “sGW”). Each Node B may be in radio contact with multiple user equipment (“UE”) (generally, user equipment includes mobile transceivers or cellular phones, although other devices such as fixed cellular phones, mobile web browsers, laptops, PDAs, MP3 players, and gaming devices with transceivers may also be UE) via the radio Uu interface. In this document, the abbreviation for user equipment (“UE”) will be synonymous with the abbreviation for mobile station (“MS”), and MS will be used primarily. MSs may also be cellular phones, PDAs, MP3 players, mobile web browsers, mobile PCs and the like.
The wireless communication systems as described herein are applicable to, for instance, 3GPP LTE compatible wireless communication systems, and of interest is an aspect of LTE, referred to as “evolved UMTS Terrestrial Radio Access Network,” or E-UTRAN. In general, E-UTRAN resources are assigned more or less temporarily by the network to one or more UE devices by use of allocation tables, or more generally, by use of a downlink resource assignment channel or physical downlink control channel (“PDCCH”). LTE is a packet-based system and, therefore, there may not be a dedicated connection reserved for communication between a UE and the network. Users are generally scheduled on a shared channel every transmission time interval (“TTI”) by a Node B or an evolved Node B (“eNode B”). A Node B or an eNode B controls the communications between user equipment terminals in a cell served by the Node B or eNode B. In general, one Node B or eNode B serves each cell. A Node B may be referred to as a “base station.” Resources needed for data transfer are assigned either as one time assignments or in a persistent/semi-static way. The LTE, also referred to as 3.9 G, generally supports a large number of users per cell with quasi-instantaneous access to radio resources in the active state. It is a design requirement that at least 200 users per cell should be supported in the active state for spectrum allocations up to 5 megahertz (“MHz”), and at least 400 users for a higher spectrum allocation.
In addition to support for UTRAN and in the future, E-UTRAN and MS devices presently in production and in development offer a dual-mode function. In the dual-mode function, the MS has the ability to connect to another service such as a wireless local area network (“WLAN”) over an access point (“AP”). The term WLAN here generally includes “Wi-Fi” standards such as 802.11b, 802.11g, 802.11n, Bluetooth, and other standards for accessing the public IP network over a wireless interface. APs, sometimes wireless access points (“WAPs”) are increasingly found in homes, businesses, university environments and public spaces such as cafes, hotels, libraries, and even on transit systems. As is well known, WAPs can provide an internet “hot spot” where a MS (including a laptop or notebook computer or a cellular phone with advanced features) can access the public IP network. Further, as more users rely on VoIP services for telephone and data transmissions as alternatives to traditionally “wired” telephone services over the public-switched telephone networks (“PSTN”), the dual-mode features of the MS can give the users access to their VoIP services away from home. Many users are abandoning traditionally wired telephones entirely, relying on their MS devices solely for telephone use, at home and away. Dual-mode MS devices provide additional access and features for these users.
Originally referred to as unlicensed mobile access (“UMA”), general access network (“GAN”) is the term used by the 3GPP standards for a system that enables mobile phones to make handovers between the cellular network and an IP access network such as WLAN, while carrying voice, data, both voice and data or other information. GAN allows the user of the dual-band mobile phones to access a broadband network.
By providing dual-mode support in MS, the WLAN can be used to extend the coverage of the GSM/GPRS network. In areas where the reception is poor, or the number of base stations or eNode Bs is not sufficient, the MS can register with the WLAN. The MS can provide the user a seamless experience since the user will still be able to access all the voice and data functions in the same manner as if the MS were using the E-UTRAN or UTRAN cellular network. The addition of support for GAN services in the MS should have a minimum impact on the efficiency and operation of the remaining services in the environment, the other MSs, the eNode B devices, the E-UTRAN mobile management entities (“MMEs”), the generic access network controllers (“GANC”) for the GAN support and other resources in the system.